[Hypnotoad]

So my 2012 Juke's AC started acting up months ago. Had my usual mechanic take a pass it. He replaced some valve (he doesn't speak good english, I heard "benson" valve, but I think he was trying to say "expansion" valve). He also recharged the AC system. No effect.

Took it to the local Nissan dealer. They had it two days and called in a specialist from LA to help diagnose it. Here's what they told me:

1. Compressor is supposed to be at 0.88 pounds, instead it's at 1.88 pounds. I'm a little confused by this, do they mean PSI? Anyway, they think the system is over pressurized and may have damaged the compressor. However given that it's been behaving this way prior to the recharge I doubt this is the root cause. They wanted $1400 to do the compressor.

2. They said the in car thermistor needs to be replaced and was reading 38F so the AC was being shut off immediately. They wanted $1900 to replace the thermistor since they "had to tear apart the entire dash".

I wasn't going to spend nearly $4k to fix the AC so I picked up the car and ordered the thermistor. Took me an entire 20 minutes to pull the panel under the stearing wheel off and swap the thermistor. The old thermistor did not look damaged. I measured both thermistors' resistance with a multimeter. They did not measure the same resistance (old one was 2.4 kOhm, new one was I think closer to 2 kOhm) so maybe it was bad... I don't know.

But it didn't fix my problem.

I'm going to re-read the HAC part of the service manual. But I'm not really sure what to do next other than try to find a shop that is good with this stuff but won't charge a crazy amount. I'm also concerned the dealer wasn't able to diagnose this correctly so a regular mechanic won't have a good chance of fixing it.

Anything easy I should look at before I take it in again? I've already had my car in the shop a total of 4 days for this, at this point I need a 2nd car or something. I'm also debating just letting the Juke go rather than pour money into it. It's only worth maybe $5k. I haven't spent any money on it up to this point so it's not like it's a maintenance problem but, I dunno, I don't necessarily need to be driving a 10 year old car. I have however been doing ridiculous things to the exterior and wasn't planning on letting it go any time soon up til now.

All advice appreciated...

 

[Bargeld]

My first thought is to run through the FSMs step by step to diagnose.

 

[Macgyver]

Lots of failed temp switch problems. There are some cheaper parts you can throw at it to see if it magically fixes it.

 

[Hypnotoad]

Lots of failed temp switch problems. There are some cheaper parts you can throw at it to see if it magically fixes it.

Which switch are you referring to?

 

[Macgyver]

The FSM does a great job of having charts, parts, and clues on what to look for.

Refrigerant Pressure Switch. On top of the Liquid tank on the side of the confessor.

The Ambient temp switch is what I was referring to.

There are a lot but use the search function here and see what you can find out that others have had done.

 

[KinKin]

This is what you are looking for:

27722-3RA0A - Ambient Air Temperature Sensor. A sensor that reads outside air - Genuine Nissan Part

Genuine Nissan Part # 27722-3RA0A (27722-15U00, 277223RA0A) - Ambient Air Temperature Sensor. A sensor that reads outside air temperature

parts.nissanusa.com

Not a juke but similar:

 

[Hypnotoad]

Well today's activities so far:

1. Borrowed a manifold gauge and measured the refrigerant pressures. Low side is 95 PSI and high side 100 PSI with AC off. When AC clutch engages, low drops to about 60 and high rises to 130, but only briefly before AC cuts out again. Oh and the dealer service guy had said the system was over pressurized -- I have no idea why they would say that.

2. Took the front end apart enough to get at the refrigerant pressure sensor. Disconnected the connector, jumpered the wires so I can measure the voltage during operation. Reading 1.1V which is about 105 PSI -- definitely in range and agrees with the manifold gauge. Also with this sensor disconnected the clutch never engages.

So I'm concluding the system is properly pressurized and the pressure sensor and its wiring are both good.

Next up I need to check out the intake sensor. It apparently cuts the AC when below 36 F.

 

[Hypnotoad]

Anyone happen to know how easy it is to get at the AC relay itself? I kinda sorta want to just bypass all the ECM stuff and put this on a manual switch. That will get me by until I feel like buying a new car (eyeballing the new Integra, but it's not out yet).

 

[Macgyver]

The AC relay is in the IDPM which is to the right of the battery. Thusly bypassing all the IDPM, BCM, ECU, sensor inputs. I dont know if a simple relay bypass will work.

HAC-10 has a good chart on what works and why.

Some quick things to try:

Check fuse num 15 in the driver side fuse panel. 10 amp one.

Check for chewed wires somewhere in the engine bay.

Is your AC Engine bay Fan working ? A malfunctioning fan will kill the compressor.

It is possible for the BCM to be bad from what I have read.

 

[Hypnotoad]

The dealer checked this over for a couple days. I hope they would have caught things like blown fuses and chewed wires. But will have a look. (edit: fuse is fine)

Not sure exactly where the compressor fan is but again, you'd think the dealer would have inspected that. I can't get the compressor to stay on for more than a few seconds so not sure I can really evaluate the fan situation.

The IPDM is under my intake so I haven't had a look at it yet. But I see the compressor clutch input is on the underside of the car and somewhat easy to get at (I think I can get a hand up in there). If I knew the connector type and polarity I could fabricate a harness and run that to a switch in the cabin. Ugh, what a pain though. And while it may be as simple as that, who knows, the whole control system may freak out.

 

[Macgyver]

Yeah I dont know. I did that on my sons 1990 Buick. It worked til the compressor locked up and the v-belt started smoking. LOL

 

[Hypnotoad]

Is it ok for the compressor to be engaged all the time while AC is blowing? Or does it need to be duty cycled? It's much more of a pain but I can rig up a little Arduino type controller to duty cycle it if needed.

Ordered a plug off ebay so... if I can get that damned connector unplugged I'll be able to at least jury rig this and get the compressor on, then I can see if the AC fan is staying on.

 

[Macgyver]

I dont know.

I think modern AC cycle to save gas.

My sons locked up cause the compressor was shot. But it was fun to see that happen.

 

[Hypnotoad]

Well, got a connector off eBay, ran a wire from the compressor to a switch in the dash to an unused fuse slot in the cabin fuse box. Wish I’d known about those fuse extender things.

Works ok. Computer seems to get confused if I switch it on when idling and the engine stalls. But otherwise is seems fine.

So…problem solved, I guess. I got a switch with an LED which is important because if I leave it on while the car is off it will drain the battery eventually.

 

[Macgyver]

Well, got a connector off eBay, ran a wire from the compressor to a switch in the dash to an unused fuse slot in the cabin fuse box. Wish I’d known about those fuse extender things.

Works ok. Computer seems to get confused if I switch it on when idling and the engine stalls. But otherwise is seems fine.

So…problem solved, I guess. I got a switch with an LED which is important because if I leave it on while the car is off it will drain the battery eventually.

Thats a decent fix.

Does the engine stall if you have the AC on while driving and then come to idle?

 

[Hypnotoad]

I haven't had more issues with it stalling. I think it stalled when I was idling and engaged it. My Juke has always had a weird thing where it will idle really low (500 RPM) and seem to struggle to stay that high. Never once has it stalled but it may just not have a lot of headroom at idle to buffer the AC engagement.

Glad this sorted out. I was at a point where I didn't want to dump a lot of money into this car, two good mechanics were telling me they couldn't figure this out, and the dealer wanted thousands and also appear to be incompetent or liars (probably the former).

So now I can get back to my ridiculous DIY wrap job.

 

[Macgyver]

I haven't had more issues with it stalling. I think it stalled when I was idling and engaged it. My Juke has always had a weird thing where it will idle really low (500 RPM) and seem to struggle to stay that high. Never once has it stalled but it may just not have a lot of headroom at idle to buffer the AC engagement.

Glad this sorted out. I was at a point where I didn't want to dump a lot of money into this car, two good mechanics were telling me they couldn't figure this out, and the dealer wanted thousands and also appear to be incompetent or liars (probably the former).

So now I can get back to my ridiculous DIY wrap job.

It works. Thats all that matters.